I did my Physics degree thesis on computing with Transputers. As part of that I got 3 Transputers (T425 I think) and I designed and built a board to house them

I did my Physics degree thesis on computing with Transputers. As part of that I got 3 Transputers (T425 I think) and I designed and built a board to house them plus an interface to the BBC micro computer which acted as the host. We didn't have the budget for any of the software tools (like the Occam compiler) so I the first thing I had to do was write an assembler. Transputer instructions are all variable length, with parameters being encoded as variable integers. So if you wanted to jump a few bytes away it would be a 1 byte instruction but you'd need a 2 byte instruction to jump further away then a 3 byte instruction etc. This meant that the assembler needed lots of passes to work as it wasn't clear how many bytes each jump instruction would take. In fact it could take up to 7 passes until the program converged into a stable state with each jump the shortest length. I wrote the assembler in BBC BASIC and due to the fact the BBC Micro had very little memory it worked on (floppy) disk rather than in memory. Floppy disk! This made it probably the slowest assembler in the world - my largest programs would take 10 minutes or more of disk chunking before they could be assembled. Once I'd written the assembler I used it to write a boot loader which configured the Transputers and loaded itself around the whole network of Transputers. Transputers could boot each other so I only needed to write the boot loader to the one the BBC micro was connected to and it would run and copy itself to the other Transputers it found, figuring out the topology of the network as it went. Once the boot loader was loaded then I could run the application. I did two, one a Mandelbrot set generator (of course!) which displayed the images on the BBC micro, and the other a physics simulation of an Ising spin model (which was kind of the point of all of this). I did the simulation on the university's mainframe in fortran too and the Transputer (cluster I guess you'd call it now-a-days) was faster! The Transputer was an amazing chip and so ahead of its time. I often imagine an alternate future where we have 1000s of small single core chips with their own memory rather than current SMP model. It would certainly be harder to program but I bet it would fly!